Solvent inhibitor for the acid treatment of metals



Z252. COMPOSITIONS,

Patented Dec. is, 1930 UNITED STATES PATENT OFFICE WILLIAM S. CALCOTT, OF PEN NS GROVE, NEW JERSEY, AND IRA E. LEE, WILMING- TON. DELAWARE, ASSIGN OBS TO E. I. DU PONT DE NEMOUBS & COMPANY, OF WIL- MINGTON, DELAWARE, A CORPORATION OF DELAWARE SOLVENT INHIBITOR FOR THE ACID TREATMENT OF METALS 1T0 Drawing. Application filed April 17, 1929. Serial No. 355,978.

This invention relates to the acid treator blank sulphuric acid solution, dissolved ment of metals. It has been known for some 100 parts of free metal during the same time time that oxides, salts, rust and other corroin which the sulphuric acid solution containsion products may be removed from the mg thio phenol dissolved 3.9 parts of free 5 surfaces of metals by suitable treatment in an acid bath. One of the disadvantages connected with such a treatment of a metal has been the degree to which the acid bath attacked the free metal in addition to the unwanted with repect to desirable qualities as inhibitors.

We have found that certain mg cgp tans possess to a very marked degree the desirable 26 properties of inhibiting the action of acids upon metals, while permitting the acids to attack undesirable corrosion products. The inhibiting quality is possessed to a very marked degree by mercaptans of the class metal. Translated to terms of percentage, the

thio phenol inhibited the solution of the metal to the extent of 96.1%.

Under the same conditions employing the same amounts of difi'ering mercaptans, the

hibiting properties.

The mercaptans may be emplo ed as inhibitors with advantage in a num er of operations, as for example, in the commercial of iron and steel, in the removal of rust of corrosion products from the interior of pipin where it is inconvenient to dismantle t e iping, in the preparation of metals for electroplating where it is desir- RSH in which R is either an alk 1 ar I able to remove oxides and other corrosion nififfiis. The eifect-iveness as inhibitors varies somewhat with the particular mercaptan, the concentration of acid, the kind of acid, the kind of metal, and the temperature at which ing action, however, is not restricted to any the acid solution is maintained. The inhibitproducts without removing the free metal and particularly without injuring the surface of the metal. We have found the merca tans to be very efficient inhibitors where emp oyed in the acid treatment of ferrous metals.

The amount of inhibitor employed will, of

1 desirable corrosion products. For the purfollowing results were obtained: poses of inhibiting this solvent action on the per cent free metal certain types of substances have Memptan nhi ition been heretofore added to the acid bath. EX- i ghenol I amples of such inhibitors are mouldy flour, B 10 naphthol '15 size or glue, the sulfonation productof h enz} lmercaptan 99'93 o5 slaughter house Waste,t e :1 ex rac OfCOa amy mercaptan 99'93 udo' ffgfifflmsulfuric acid treatment PIOPY1 mercaptan 99-84 oca ar orp troleum, carbazole, pyridine, Amino substituted mercaptans, such as 2- aniline quinoline, e 0. None of t ese su amino-5-ethoxy-thiophenol and 1-mercapto- 2o stahbesfhowever, afford all that o ld e 2-amino-anthraquinone show satisfactory in- 7 particular mercapta-n or to any particular course, vary in accordance with the requirecondition of concentration temperature or ments of the operator. For example, in the kind of acid. Under all conditions the rate of pickling of heavy, cheap materials, such as,

solution of the free metal is materially reduced.

As an example of the effectiveness of mercaptans, mild steel was treated with an aqueous solution containing 5% sulphuric acid; the acid bath was maintained at a temperature of C. Two samples of equal weight from the same batch of steel were treated in two separate acid solutions under the above conditions, and to one of the solutions was added 0.03% of thio phenol. The untreated,

for instance, iron castings, an inhibition of 75 to might be quite satisfactory to the pickler, while in the case of relatively valuable material, such as the finer grades of iron or seamless tubing, the pickler might be dissatisfied with less than 99% or even better inhibition. The amount of inhibition varies somewhat with the kind and amounts of inhibitor employed, although any measurable quantity of inhibitor will produce some retardation of solution.

,....lh1bitoris--used. Nor

It is sometimes advantageous to mix with the inhi a substance which will cause the f presence of inhibitors. this ably e may accomplish by using with the inhibitor, and prefermixing with it before addition to the acid, a metallic chloride such for example as sodium chloride, in such quantity that hydrochloric acid will be formed in amounts sufiicient to substantially reduce the time required for pickling.

e do not wish to be limited to the specific mercapta-ns listed above, which it should be understood are given only as examples; nor do we wish to be limited to the amounts of inhibitor or conditions under which the indo we wish to be limited to any particular acid since any acid normally useful in pickling operations may be employed. On the contrary, we desire our invention to be limited only as defined in the appended claims.

e claim:

1. The process of treating metals which comprises subjecting the metal to an acid solution containing a mercaptan of the type:

pound of the type R-H in which R is a hydrocarbon S atom.

4. The process of treating ferrous metals which comprises subjecting the metal to a sulphuric acid solution containing a mercaptan compound of the type RS in which R is a hydrocarbon group directly attached to the S atom.

5. In the pickling of metals the step which comprises subjecting the metal to an acid bath containin a mercaptan compound of the type 12-8 in which R is a hydrocarbon group directly attached to the S atom.

6 A solution of the type adapted for the acid treatment of metals which contains a mercaptan of the type:

group directly attached to the 7. A solution of the type adapted for the acid treatment of metals which contains a mercaptan of the type RSH in which R is a hydrocarbon group directly attached to t e S atom.

8. A solution of the type adapted for the acid treatment of ferrous metals which contains a mercaptan of the type R-SH in which R is a hydrocarbon group directly attached to the S which mercaptan.

11. The process of treating ferrous metals which comprises subjecting the metal to a sulphuric acid solution containing iso-propyl Y tures.

WILLIAM S. CALOOTT. IRA E. LEE.

the type adapted for metals which contains 

